In one example form of video signal processing, a noise reduction function is applied to reduce noise in a video signal. Noise reduction processing can be applied in a sequential order, first to a luminance component of the video signal, and then to chrominance components of the video signal. Conveniently, the same noise reduction circuit is used for both the luminance and chrominance components of the video signal. Optionally, in luminance controlled processing, a control signal is derived from the luminance component and written to a background memory during processing of the luminance component, and read from the background memory for use during the subsequent processing of the chrominance components. This luminance-derived control signal can also be used in other forms of video signal processing. A problem arises in that storage of the control signal involves a relatively large quantity of data. For example, in a typical prior art system the luminance-derived noise reduction control signal has a quantization of seven bits, such that one byte of data storage is required for each pixel in the video signal.